Our long-term objective is to understand the number, control and interactions of all gene products involved in the various stages leading to S. mutans pathogenicity including sucrose-independent and dependent adherence, aggregation, complex carbohydrate biosynthesis, and carbohydrate metabolism and acid production. Our initial efforts will be directed at those gene products which influence those processes which occur on the S. mutans cell surface. Specifically, we will : 1) isolate new mutants of S. mutans with genetic defects in the synthesis or placement of known protein products by (i) introducing defective S. mutans genes that had been previously cloned into and characterized in Escherichia coli K-12 strains and (ii) selecting mutants for the absence of cell surface protein products by using antibodies directed against specific S. mutans gene product expressed by E. coli recombinant clones; 2) characterize both existing and newly isolated mutants for (i) presence of cell surface protein products using immunological techniques and antisera raised against such proteins expressed by E. coli recombinants, (ii) ability to adhere (both sucrose-dependent and sucrose-independent), aggregate and produce acid, (iii) presence of enzymes such as glucosyltransferase, fructosyltransferase, dextranase and invertase, (iv) ability to complement each other for adherence, aggregation and plaque formation during mixed cultivation or incubation; and (3) evaluate the virulence of mutants alone and in combination for complementing mutants in gnotobiotic rats.